The manufacture of higher olefins from ethylene is a well known art. The resulting olefins are subsequently used to prepare a wide variety of products including detergents, synthetic lubricants, and high molecular weight polymers and copolymers. Ethylene is a comparatively expensive material, so the use of alternative feedstocks such as propylene, butene or butadiene has also been investigated.
For example, U.S. Pat. No. 4,356,333 (Yoshimura et al.) discloses the dimerization of butadiene in an aqueous sulfolane solution, using a palladium catalyst, to product n-octadienol. This normal alcohol is useful for the manufacture of various synthetic resin modifiers and chemicals. It may also be selectively hydrogenated to n-octanol (which is useful in the synthesis of di-n-octyl phthalate which, in turn, is used as a plasticizer). Finally, the n-octanol may be dehydrated to produce octene. Thus, the synthesis of octene from butadiene involves three steps—dimerization, selective hydrogenation and dehydration.
It will be appreciated by those skilled in the art that each of the above described steps in the synthesis of octene from butadiene needs to be executed in an efficient manner in order to optimize the production of octene.
Similar processes have been reported in the patent literature. For example, U.S. Pat. No. 4,234,752 (Wiu et al.) disclosed the dehydration of alcohols in the presence of gamma-alumina. The gamma-alumina is preferably treated with a base.
Similarly, the abstract of German Patent 3,915,493 (assigned to Metallgesellschaft AG of Germany and Godrej Soaps Ltd. of India), discloses the synthesis of olefins from fatty alcohols in the presence of alumina which has been treated with ammonia.
World Patent application WO 2004/052809 (assigned to Oxeno) teaches the preparation of olefins from ethers using an alumina (with alkali or alkaline earth metal oxide) catalyst.
Finally, U.S. Patent application 2003/0065233 (assigned to Kuraray) discloses the synthesis of olefins from ethers or alcohols using alumina which has been treated with an organic amine.
However, the prior art does not disclose the conversion of ethers to olefins in the presence of ammonia. We have now discovered that olefins may be very efficiently produced from ethers using an alumina catalyst which has been treated with ammonia.